Flow restricting deflector

ABSTRACT

Drag reducing systems for vehicles are provided. In one aspect, a drag reducing system generally includes a flow restricting deflector couplable to a mount and positioned upstream in a path of airflow to an object. The flow restricting deflector generally includes a body portion and a plurality of flow choking orifices configured to provide a choked airflow condition. In another aspect, the drag reducing system is configured for positioning adjacent a wheel and tire combination of a vehicle upstream in a path of airflow to the wheel and tire combination. The flow restricting deflector may be coupled to and extending downward from a splash shield adjacent the wheel and tire combination.

BACKGROUND

Numerous means have been sought to improve the fuel-efficiency of movingbodies and, especially, moving bluff bodies by reducing theiraerodynamic drag. In the field of surface transportation, andparticularly in the long-haul trucking industry, even small improvementsin fuel efficiency can reduce annual operating costs significantly. Itis therefore advantageous in the design of a vehicle to reduce dragforces, thereby increasing the aerodynamic properties and efficiency ofthe vehicle.

The over-the-highway cargo-hauling tractor-trailer combination is onevehicle that experiences excessive aerodynamic drag. Generallydescribed, tractor-trailer combinations typically include a tractorhaving a so-called fifth wheel by which a box-like semi-trailer may beattached to the tractor by an articulated connection for transportationof the cargo trailer. Conventional tractors may include tandem (dual) ortridem (triple) rear axles, where two or three sets of axles arepositioned close together along the length of the tractor, near thefifth wheel, to carry the weight of the trailer. Conventional trailersalso may include tandem or tridem axles.

It is well known that bluff bodies, such as tractors and trailers,contribute significantly to aerodynamic drag, as evidenced by theformation of a wake along the length of and in the trailing regionbehind the trailer. Additionally, various components of the tractors andtrailers, such as the wheels and tires, also contribute significantly tothe aerodynamic drag of the vehicle. The generation of eddies can becontributed to the shape and rotation of the wheels and tires as thevehicle is driven down the road, especially at freeway speeds. Airflowaround the rotating wheels and tires forms eddies, creating significantturbulence and increasing drag to reduce vehicle efficiency. The netresult is the creation of considerable aerodynamic drag.

SUMMARY

In accordance with one embodiment of the present disclosure, a dragreducing system is provided. The drag reducing system generally includesa flow restricting deflector couplable to a mount and positionedupstream in a path of airflow to an object. The flow restrictingdeflector generally includes a body portion; and a plurality of flowchoking orifices extending through the body portion. Each flow chokingorifice has an inlet, an outlet, and an interior wall configured toprovide a choked airflow condition.

In accordance with another embodiment of the present disclosure, a dragreducing assembly for a vehicle is provided. The drag reducing assemblygenerally includes a mounting bracket and a splash shield coupled to themounting bracket. The splash shield is positioned adjacent a wheel andtire combination of the vehicle. A flow restricting deflector is alsoprovided, and is coupled to and extending downwardly from the splashshield. The flow restricting deflector is positioned upstream in a pathof airflow to the wheel and tire combination. The flow restrictingdeflector generally includes a body portion and a plurality of flowchoking orifices extending through the body portion. Each flow chokingorifice having an inlet, an outlet, and an interior wall configured toprovide a choked airflow condition.

In accordance with any of the embodiments disclosed herein, the interiorwall may have a slope such that the flow choking orifice is larger inarea at the inlet than at the outlet to constrict the airflow.

In accordance with any of the embodiments disclosed herein, the slope ofthe interior wall may be linear.

In accordance with any of the embodiments disclosed herein, the slope ofthe interior wall may be concave curvilinear.

In accordance with any of the embodiments disclosed herein, the slope ofthe interior wall may be convex curvilinear.

In accordance with any of the embodiments disclosed herein, the dragreducing system may further include a splash shield extending from anupper edge of the body portion. In these and other embodiments thesplash shield has a surface positioned adjacent a wheel and tirecombination of a vehicle.

In accordance with any of the embodiments disclosed herein, a ratio ofwidths of the plurality of flow choking orifices to the width of thesolid portions of the body portion may be between about 3 and 9.

In accordance with any of the embodiments disclosed herein, a ratio ofwidths of the plurality of flow choking orifices to the width of thesolid portions of the body portion may be between about 5 and 7.

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thepresent disclosure will become more readily appreciated as the samebecome better understood by reference to the following detaileddescription, when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 is a side view of a conventional cargo-type trailer;

FIG. 2 is a front perspective view of one representative embodiment of adrag reducing system formed in accordance with aspects of the presentdisclosure, showing a splash shield and a flow restricting deflector;

FIG. 3 is a cross-sectional bottom view of the flow restrictingdeflector of FIG. 2, showing representative airflow through flow chokingorifices of the flow restricting deflector; and

FIGS. 4A-4C are cross-sectional detail views of the interior wall shapeof the flow choking orifices of FIG. 3.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings, where like numerals reference like elements, are intended as adescription of various embodiments of the present disclosure and are notintended to represent the only embodiments. Each embodiment described inthis disclosure is provided merely as an example or illustration andshould not be construed as precluding other embodiments. Theillustrative examples provided herein are not intended to be exhaustiveor to limit the disclosure to the precise forms disclosed.

In the following description, specific details are set forth to providea thorough understanding of exemplary embodiments of the presentdisclosure. It will be apparent to one skilled in the art, however, thatthe embodiments disclosed herein may be practiced without embodying allof the specific details. In some instances, well-known process stepshave not been described in detail in order not to unnecessarily obscurevarious aspects of the present disclosure. Further, it will beappreciated that embodiments of the present disclosure may employ anycombination of features described herein.

The present application may include references to directions, such as“forward,” “rearward,” “front,” “rear,” “upward,” “downward,” “top,”“bottom,” “right hand,” “left hand,” “lateral,” “medial,” “in,” “out,”“extended,” etc. These references, and other similar references in thepresent application, are only to assist in helping describe and tounderstand the particular embodiment and are not intended to limit thepresent disclosure to these directions or locations.

The present application may also reference quantities and numbers.Unless specifically stated, such quantities and numbers are not to beconsidered restrictive, but exemplary of the possible quantities ornumbers associated with the present application. Also in this regard,the present application may use the term “plurality” to reference aquantity or number. In this regard, the term “plurality” is meant to beany number that is more than one, for example, two, three, four, five,etc. The terms “about,” “approximately,” “near,” etc., mean plus orminus 5% of the stated value. For the purposes of the presentdisclosure, the phrase “at least one of A, B, and C,” for example, means(A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C),including all further possible permutations when greater than threeelements are listed.

The over-the-highway cargo hauling tractor-trailer combination is onevehicle that experiences excessive aerodynamic drag. Generallydescribed, tractor-trailer combinations typically include a tractor 18having a so-called fifth wheel by which a box-like semi-trailer 24 maybe attached to the tractor 18 by an articulated connection fortransportation of the cargo in the trailer 24, as shown in FIG. 1. Theshape of the conventional tractor-trailer combination provides numerousareas for aerodynamic inefficiency. In one aspect, the trailer 24 isessentially a rectangular box having a flat, rectangular roof 38 andmatching floor 40, along with flat, rectangular side panels 42. The foreand aft vertical surfaces 44 and 46, respectively, of such trailers 24are also generally flat rectangular surfaces. The aft section of thetrailer 24 is supportably mounted on one or more wheel assemblies,illustrated as components 52 and 54.

Conventional large long-haul cargo trailers similar to those describedabove exhibit less than optimal aerodynamic performance during highwayoperation. At highway speeds, the components of the tractor-trailercombination develop a substantial amount of turbulent airflow throughoutregions of the vehicle. This turbulence results in significantaerodynamic drag, increasing both fuel consumption and Nitrogen Oxide(NOx) emissions of the tractor 18.

Forward facing surfaces of bluff bodies draw considerable attention inaerodynamic designs. The forward surfaces are generally shaped withsmooth transitions to provide for gentle diversion of the airflow aroundthe bluff body. In some applications, such as with tandem (dual) andtridem (triple) drive and trailer axles, there is insufficient clearanceforwardly of the forwardmost axle to provide for a smooth aerodynamictransition around the wheels and tires of the drive axles. In theseexamples, pressure drag forces simply transfer from the object beingshielded (e.g. the wheels and tires), to the shield itself, generallyresulting in a zero net aerodynamic drag improvement. Although theembodiments disclosed herein are described in reference to systems anddevices that deflect airflow around the wheels and tires of the tandemor tridem rear axles of a vehicle, such a tractor or trailer, thedisclosure should be construed as applying to any suitable positionwhere flow deflection is desired.

In fluid dynamics, choked flow is a compressible flow effect limitingthe airflow velocity based on the venturi effect. When a flowing fluidat a given pressure and temperature passes through a restriction (suchas an orifice of a restriction plate) into a lower pressure environment,the airflow velocity increases. At upstream airflow conditions when thevehicle is traveling at highway speeds, the conservation of massprinciple requires the airflow velocity increase as it flows through thesmaller cross-sectional area of the orifice of the flow restrictiondeflector. At the same time, the venturi effect causes the staticpressure, and therefore the density, to decrease downstream beyond therestriction deflector. Choked flow is a limiting condition where themass flow will not increase with a further decrease in the downstreampressure environment while upstream pressure is fixed, e.g., at a fixedvehicle speed. Choked flow provides an upstream pressure buildup, aswill be explained in greater detail below.

Embodiments of the present disclosure comprise drag reducing systems inthe form of flow restricting deflectors configured to deflect air aroundthe wheels and tires by means of flow choking restriction throughorifices in the deflector, rather than by surface stagnation occurringwith a deflecting surface without orifices. By applying flow resistanceupstream of the bluff body through flow choking restriction of thedeflector, high speed freestream flow (i.e., airflow that does nottravel through orifices in the deflector or otherwise stagnate on asurface) is diverted around the bluff body by the pressure buildup onthe upstream side. Pressure rise resulting from the airflow choking atan orifice of the deflector does not cause pressure drag in areas wheredeflector material is cut out. As a result, a deflector having flowchoking orifices yields lower pressure drag than a conventional soliddeflector, while continuing to provide similar airflow diversion aroundthe object being shielded.

The following discussion provides examples of systems and methods forimproving the aerodynamic efficiency (e.g., reduce drag) of vehicles,such as class 8 tractor-trailer combinations. To improve the aerodynamicefficiency of the combination, examples described herein provide one ormore aerodynamic components positioned in the airflow stream forward ofthe outer components of the rear axles (generally, wheels and tires). Insome examples described herein, the one or more aerodynamic componentsare in the form of flow restricting deflectors, which may be used inconjunction with a splash shield. In configurations where space betweenthe wheels and tires and other components of the tractor, such as fueltanks, is limited, particularly the tandem and tridem rear axlecombinations, the flow restricting deflector may be suitably positionedupstream of the wheels and tires to reduce the total aerodynamic drag ofthe vehicle.

Turning to FIG. 2, a perspective view of one example of an aerodynamicsystem is shown, generally denoted as a drag reducing system 100, havinga flow restricting deflector 110, according to aspects of the presentdisclosure. The flow restricting deflector 110 is shown in a positionupstream and in an airflow path from the front of the tractor 18 towardthe wheels W and tires T of the rear axle of the tractor 18. In theillustrated embodiment, the rear axles (not shown) are in a tandemconfiguration having dual wheels W and tires T per axle outer end. Inother embodiments, the rear axles may be in a single axle configuration,tridem axle configuration, or any other axle configuration. Likewise, insome embodiments, the rear wheel configuration includes large, singletires known as super-singles, which are also within the scope of thepresent disclosure.

As shown in FIG. 2, the tractor 18 and trailer 24 are positioned abovethe drag reducing system 100. In some configurations of the tractor 18,a fuel tank FT is positioned under the cab and/or sleeper portion of thetractor 18 along the frame rail FR. As illustrated, the fuel tank FT maybe positioned near the forward axle of the tandem configuration, suchthat a smooth transition aerodynamic element does not have enoughclearance to be located between the fuel take FT and the wheels W andtires T of the forward tandem axle. The embodiments of the presentdisclosure address the limited clearance of many tractor componentlayout configurations. In this regard, in other configurations, anycomponent of the tractor may be located near the drag reducing assembly100, such as access steps, air tanks, battery boxes, no-idle systems,etc.

The drag reducing system 100 includes the flow restricting deflector110, which, in some embodiments, is coupled to a spray shield 130. Inthe embodiment shown, the spray shield 130 mounts to the frame rail FRwith a mounting post 132, and optionally includes an upper extension 134to direct airflow above the tires T. The spray shield 130 and optionalupper extension 134 are positioned to prevent spray and debris from therotating tires T to be carried through the rotation and released to bepropelled forward into the tractor 18, the fuel tank FT, or any othercomponent of the vehicle. The spray shield 130 is generally shaped toconform to the tires T such that the airflow contacting the spray shield130 is generally directed around the sides of the spray shield 130,around the wheels W and tires T, and up over the upper extension 134above the wheels W and tires T. Conventional spray shields comprise asolid panel without openings to block the spray and debris from therotating tires T to contact the components of the vehicle. In thisregard, as explained above, airflow impacting the spray shield 130 maystagnate and provide a high-pressure region assisting in directing theairflow around and above the spray shield 130.

In the embodiments disclosed herein, the lower portion of the sprayshield 130 includes the flow restricting deflector 110 extending downtoward the ground in front of the wheels W and tires T. The flowrestricting deflector 110 includes a plurality of flow choking orifices120 positioned along the surface of the flow restricting deflector 110.In the embodiment shown, twelve rectangular flow choking orifices 120are positioned along the surface of the flow restricting deflector 110.However, in other embodiments, any number and shape or size of flowrestricting orifice is within the scope of the present disclosure, suchas rounded, circular, oval, triangular, polygonal, and the like. Theposition of the flow restricting deflector 110 with respect to the sprayshield 130 allows for the flow choking orifices 120 to be sized andshaped for the desired aerodynamic characteristics, without compromisingthe prevention of the spray and debris from the rotating tires T to bepropelled forward into the tractor 18. Spray and debris from the tires Timpacting the flow restricting deflector 110 would be directed at anangle as to not travel through the flow choking orifices 120 toward thetractor-trailer combination. Although the flow restricting deflector 110is shown with a forward convex curvature generally following the arc ofthe splash shield 130 and tires T, in other embodiments, the flowrestricting deflector is planar, multi-planar, a complex curved surface,or any other suitable surface shape.

Turning now to FIG. 3, the aerodynamic flow characteristics of the flowrestricting deflector 110 will now be explained in greater detail. Asthe inlet airflow 140 approaches the flow restricting deflector 110, itmay be relatively uniform in flow characteristics, such as flow rate,temperature, density, and pressure. However, due to the complexity ofthe components positioned in front of the flow restricting deflector110, the inlet airflow 140 may not be uniform due to certain vehicleconfigurations and environmental inputs. In this regard, the inletairflow 140 is shown in a uniform matter for simplicity in the followingdescription, but the control of non-uniform airflow is also within thescope of the present disclosure.

As certain streams of the inlet airflow 140 approach the flowrestricting deflector 110, the stream may be aligned with one of theflow choking orifices 120 such that the stream flows through the flowchoking orifice 120, increases in velocity, decreases a pressure, andforms a through-orifice airflow 150. The pressure differential from theinlet side of the flow choking orifice 120, to the outlet side, causespressure buildup on the inlet side and an increased pressure area 142 infront of the flow restricting deflector 110. Due to the fluid dynamiccharacteristics of the airflow 140, the increased pressure area 142 mayhave generally parabolic shaped sections near the edges of the flowrestricting deflector 110. As a result, some of the streams of the inletairflow 140 will interact with the increased pressure area 142 and bedirected around the flow restricting deflector 110. The deflectedstreams of the inlet flow 140 form a diverted airflow 152.

As described above, a solid surface without orifices would provide adeflection of the inlet airflow around the surface; however, theaerodynamic benefit of the through-orifice airflow 150 would not berealized in such a configuration. In the embodiments of the flowrestricting deflector 110, the through-orifice airflow 150 and thediverted airflow 152 create a net decrease in aerodynamic drag of thevehicle between 0.2% and 2.0%. In other embodiments, the through-orificeairflow 150 and the diverted airflow 152 create a 1% net decrease inaerodynamic drag of the vehicle.

As viewed from the perspective of FIG. 3, the flow choking orifices 120comprise a ratio of the overall width of the flow restricting deflector110. In some embodiments, the ratio of flow choking orifices 120 tosolid material width of the flow restricting deflector 110 is betweenabout 3 and 9. In other embodiments, the ratio of flow choking orifices120 to solid material width of the flow restricting deflector 110 isbetween about 5 and 7. In a similar manner, each flow choking orifice120 comprises a width. In some embodiments, the width of the flowrestricting deflector 110 is between about 22 inches and 28 inches. Inthese embodiments, the maximum width of each flow choking orifice 120 isabout 6 inches. A frontal open area is defined as percentage of thetotal flow choking orifice area to the overall area of the flowrestricting deflector. In this regard, in some embodiments, the frontalopen area is between about 50% and about 99%. In other embodiments, thefrontal open area is between about 50% and about 80%.

Turning to FIGS. 4A-4C, in some embodiments, the flow choking orifices120 may have an internal shape to enhance the venturi effect of thethrough-orifice flow 150, such that a choked flow condition is presentat the desired vehicle speeds. As shown in FIG. 3, the flow chokingorifice 120 includes an interior wall 122 that is generally flat andlinear through the thickness of the flow restricting deflector 110. Inother embodiments, the shape of the interior walls of the flow chokingorifice 120 may be linear, curvilinear, geometric, or any other suitableshape to provide the desired fluid dynamic characteristics at thevehicle speeds where the aerodynamic drag has a greater influence, i.e.,at freeway speeds.

In one embodiment shown in FIG. 4A, the flow choking orifice 120includes an interior wall 124 that is linearly sloping inward from theinlet to the outlet, such that the flow choking orifice 120 isconstricting as the airflow 150 travels through the flow choking orifice120. In another embodiment shown in FIG. 4B, the flow choking orifice120 includes an interior wall 126 that is convex curvilinear slopinginward from the inlet to the outlet, such that the flow choking orifice120 is constricting as the airflow 150 travels through the flowconstricting orifice 120. In a further embodiment shown in FIG. 4C, theflow choking orifice 120 includes an interior wall 128 that is concavecurvilinear sloping inward from the inlet to the outlet, such that theflow choking orifice 120 is constricting as the airflow 150 travelsthrough the flow choking orifice 120. Although several examples of theconfiguration of the interior wall of the plurality of flow chokingorifices 120 are shown, in other embodiments, any suitable interior wallshape and configuration of the flow choking orifices 120 is also withinthe scope of the present disclosure.

The principles, representative embodiments, and modes of operation ofthe present disclosure have been described in the foregoing description.However, aspects of the present disclosure, which are intended to beprotected, are not to be construed as limited to the particularembodiments disclosed. Further, the embodiments described herein are tobe regarded as illustrative rather than restrictive. It will beappreciated that variations and changes may be made by others, andequivalents employed, without departing from the spirit of the presentdisclosure. Accordingly, it is expressly intended that all suchvariations, changes, and equivalents fall within the spirit and scope ofthe present disclosure as claimed.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A drag reducing system,comprising: a flow restricting deflector couplable to a mount andpositioned upstream in a path of airflow to an object, the flowrestricting deflector comprising: a body portion; and a plurality offlow choking orifices extending through the body portion, each flowchoking orifice having an inlet, an outlet, and an interior wallconfigured to provide a choked airflow condition.
 2. The drag reducingsystem of claim 1, wherein the interior wall has a slope such that theflow choking orifice is larger in area at the inlet than at the outletto constrict the airflow.
 3. The drag reducing system of claim 2,wherein the slope of the interior wall is linear.
 4. The drag reducingsystem of claim 2, wherein the slope of the interior wall is concavecurvilinear.
 5. The drag reducing system of claim 2, wherein the slopeof the interior wall is convex curvilinear.
 6. The drag reducing systemof claim 1, further comprising a splash shield extending from an upperedge of the body portion, the splash shield having a surface positionedadjacent a wheel and tire combination of a vehicle.
 7. The drag reducingsystem of claim 1, wherein a ratio of widths of the plurality of flowchoking orifices to the width of the solid portions of the body portionis between about 3 and
 9. 8. The drag reducing system of claim 1,wherein a ratio of widths of the plurality of flow choking orifices tothe width of the solid portions of the body portion is between about 5and
 7. 9. A drag reducing assembly for a vehicle, comprising: a mountingbracket; a splash shield coupled to the mounting bracket, the splashshield positioned adjacent a wheel and tire combination of the vehicle;a flow restricting deflector coupled to and extending downwardly fromthe splash shield, the flow restricting deflector positioned upstream ina path of airflow to the wheel and tire combination, the flowrestricting deflector comprising: a body portion; and a plurality offlow choking orifices extending through the body portion, each flowchoking orifice having an inlet, an outlet, and an interior wallconfigured to provide a choked airflow condition.
 10. The drag reducingassembly of claim 9, wherein the splash shield and flow restrictingdeflector have a width configured to cover a dual wheel and tirecombination.
 11. The drag reducing assembly of claim 9, wherein theinterior wall has a slope such that the flow choking orifice is largerat the inlet than at the outlet to constrict the airflow.
 12. The dragreducing assembly of claim 11, wherein the slope of the interior wall islinear.
 13. The drag reducing assembly of claim 11, wherein the slope ofthe interior wall is concave curvilinear.
 14. The drag reducing assemblyof claim 11, wherein the slope of the interior wall is convexcurvilinear.
 15. The drag reducing assembly of claim 9, wherein a ratioof widths of the plurality of flow choking orifices to the width of thesolid portions of the body portion is between about 3 and
 9. 16. Thedrag reducing assembly of claim 9, wherein a ratio of widths of theplurality of flow choking orifices to the width of the solid portions ofthe body portion is between about 5 and 7.